1. Field of the Invention
This invention relates to compositions useful for injecting into subterranean reservoirs to recover crude oil therefrom and more specific to petroleum sulfonates obtained by reacting aromatic hydrocarbon gaseous SO.sub.3.
2. Description of the Prior Art
Petroleum sulfonates have been prepared by a variety of means, for example, sulfonated with sulfur dioxide (U.S. Pat. No. 2,999,812), sulfur dioxide and chlorine (U.S. Pat. No. 2,197,800), oleum (U.S. Pat. No. 2,845,455), and sulfur trioxide (U.S. Pat. No. 3,183,183). U.S. Pat. Nos. 3,215,628 and 2,815,370 teach the use of specific hydrocarbon fractions. Other patents of lesser interest include U.S. Pat. Nos. 2,174,508; 2,800,962; 3,173,864; 3,308,068, 3,244,622; and 3,418,239.
The prior art suggests that whole crude oil can be sulfonated and used in oil production. (See U.S. Pat. Nos. 1,822,271; 3,126,952; and 3,302,713 teaching the use of whole crude sulfonates in secondary-type oil recovery and U.S. Pat. Nos. 2,798,851; 2,953,525; and 3,198,832 teaching the use of such sulfonates in drilling muds.) However, we are unaware of a teaching as to how this can be done or any commercial use of such a process. Specific teachings of which we are aware require the removal of the light and/or heavy ends and the use of only the middle cuts to obtain the petroleum sulfonates.
There are a number of reasons for fractionating crudes prior to sulfonation. Inter alia, it is difficult to obtain a marketable product from asphaltenes which tend to form tarry materials which foul reactors and sometimes form coke-like deposits. Also, the light ends are often aliphatics or light aromatics which will not produce the desired product.
We have now discovered that commercially acceptable sulfonates can be prepared from a variety of crude oils using our processes. While we were surprised to be able to prepare sulfonates in good yields and without coking or the formation of tarry products, we were pleased when we found that the sulfonates produced economic micellar systems suitable for use in oil recovery.
The upcoming "energy crisis" puts our invention in context. T. M. Geffen (Oil & Gas Journal, May 7, 1973, pp. 66-76) indicates that 55 billion barrels of additional crude can be recovered via tertiary recovery. Heretofore, tertiary recovery processes (see U.S. Pat. Nos. 3,254,714; 3,307,628; 3,504,744; 3,261,399; 3,497,006; 3,506,070, 3,354,953; 3,330,344 and 3,348,611--most using petroleum sulfonate surfactants) have all proved uneconomic because, inter alia, the cost of materials used made the processes uneconomic and the amounts of oil recovered were too small. Our process provides sulfonates at a price sufficiently low to aid substantially in the commercialization of tertiary oil recovery using secondary-type oil recovery techniques taught in the above-listed patents.
According to the present invention, a substantially continuous flow of sulfur trioxide in the gas phase is reacted with a hydrocarbon which can be either whole crude oil or topped crude oil or mixtures thereof. The contact occurs in a reaction zone fed by a substantially continuous flow of said hydrocarbon at temperatures, pressures, and other conditions as described hereinafter, and is followed by neutralization and possible extraction of unreacted hydrocarbons. The invention thus offers the substantial advantage of being able to produce valuable petroleum sulfonates from crude oils without fractionation (other than optional "topping" to remove low boiling fractions, usually paraffinic and not very reactive). The simplicity of this technique permits the use of portable sulfonation facilities which can manufacture petroleum sulfonates in the oil field. Thus, the present invention offers the opportunity to manufacture sulfonates for use in petroleum recovery by use of substantially untreated recovered petroleum with all of the attendant advantages over existing techniques which require substantial refining prior to sulfonation, use of selected fractions of petroleum in order to provide sulfonates suitable for preparation of micellar systems, and the transportation from the producing field to the refinery and then the sulfonation plant and thence to the point of use in the field.